1. Field of the Invention
The present invention relates to a giant magneto-resistive effect element and also relates to a magneto-resistive effect type head, a thin-film magnetic memory and a thin-film magnetic sensor including this giant magneto-resistive effect element.
2. Description of the Related Art
At present, as a high-density magnetic recording device such as a hard disk drive, there is adopted a so-called merge type composite magnetic head which is provided by combining an inductive type write magnetic head and a read magnetic head utilized a magneto-resistive effect (magneto-resistive effect type head).
FIG. 1 of the accompanying drawings is a schematic perspective view illustrating an arrangement of a merge type composite magnetic head. A gap film and an insulating film are not shown in FIG. 1.
As show in FIG. 1, a magnetic sensing element 53 is disposed on a lower shield 52 made of a magnetic material formed on a substrate 51, and an upper shield 54 made of a magnetic material is formed on an upper layer.
The lower shield 52, the magnetic sensing element 53 and the upper shield 54 constitute a read magnetic head 61 as a lower layer magnetic head. As the magnetic sensing element 53, there is used an element having a magneto-resistive effect, i.e., a magneto-resistive effect element (MR element).
The upper shield 54 serves also as a lower layer magnetic core of a recording upper magnetic head, and a tip end pole portion 55 is disposed above the upper shield 54. An upper layer magnetic core 57 is connected onto the tip end pole portion 55. Further, a back yoke 58 is connected to the rear portion of the upper layer magnetic core 57. Then, a coil 56 is disposed among the lower layer magnetic core 54, the upper layer magnetic core 57 and the back yoke 58 through an insulating layer.
The lower layer magnetic core 54, the coil 56, the tip end pole portion 55, the upper layer magnetic core 57 and the back yoke 58 constitute and inductive type write magnetic head 62 as an upper magnetic head.
Then, a merge type composite magnetic head 50 is constructed by laminating the read magnetic head 61 of the lower layer and the write magnetic head 62 of the upper layer.
As a magneto-resistive effect element (MR element) for use as a magneto-resistive effect type head comprising the read magnetic head 61 of the lower layer of this composite magnetic head 50, there is recently used a giant magneto-resistive effect element (GMR element) which can demonstrate a higher sensitivity.
The GMR element which becomes commercially available at present is used in a so-called CIP (current in plane) mode in which a sense current for detecting a magneto-resistive effect flows in the direction parallel to the film plane of the laminated layer film.
However, in the arrangement of the CIP type GMR element which is used in this CIP mode, when a recording density is further increased from now on, there will be a limit on increasing a recording density in rear future from a standpoint of electrical short-circuit between a shield film and a hard film to which the sense current flows, an electromigration and so forth.
From this background, recently, there has been examined a CPP type GMR element which may be used in a so-called CPP (current perpendicular to the plane) mode in which a sense current flows to the direction perpendicular to the film plane of the laminated layer film of the GMR element.
Since the CPP type GMR element uses a shield film as an electrode, an insulating layer between the shield layer and the GMR element can be removed, the above-mentioned problem of the electrical short-circuit can be solved fundamentally.
Moreover, since the CPP type GMR element can increase its area in which it comes in contact with an electrode film formed of a metal film having an excellent thermal conduction, this CPP type GMR element has a characteristic such that an electromigration becomes difficult to occur at a remarkably higher current density as compared with the CIP type GMR element. Therefore, it may be considered that this CPP type GMR element becomes able to realize a narrow gap and a narrow track width which are the requirements of the high density recording magnetic head.
FIG. 2 is a schematic diagram (cross-sectional view) of the GMR element which can be used in this CPP mode.
In the arrangement of the CPP type GMR element shown in FIG. 2, a conductive hard magnetic material is used as a hard magnetic film (hard film) which is useful for stabilizing the GMR element.
As shown in FIG. 2, on a lower magnetic shield 71 made of a magnetic material, there is deposited a GMR element 73 whose cross-section is a trapezoid through a lower gap film 72 made of a non-magnetic conductive material and which serves also as an electrode film. Although not shown, this GMR element 73 is comprised of a laminated layer film of a magnetic film and a non-magnetic film. On the right and left of the GMR element 73, there are disposed hard magnetic films 77 made of a conductive hard magnetic material through insulating films 76 such as alumina films. The insulating films 76 are adapted to insulate the GMR element 73 and the conductive hard magnetic films 77 from each other. On the hard magnetic films 77, there are deposited insulating layers 78 over the GMR element 73. AN upper magnetic shield 75 made of a magnetic material is disposed on the insulating layers 78 through an upper gap film 74 made of a non-magnetic conductive material. The upper gap film 74 serves also as an electrode film and is connected to the GMR element 73 through an opening (width W) defined between the right and left insulating layers 78.
The lower magnetic shield 71 and the lower gap film 72 constitute a lower electrode, and the upper magnetic shield 75 and the upper gap film 74 constitute an upper electrode. Through these lower and upper electrodes, a sense current in the direction perpendicular to the film plane of the laminated layer film can flow to the GMR element 73. Moreover, the hard magnetic film 77 can stabilize the GMR element 73 magnetically.
In the arrangement shown in FIG. 2, the respective layers can function as follows:
The lower magnetic shield 71 and the upper magnetic shield 75 can function to restrict a signal magnetic field from being entered into the GMR element 73 in order to increase a recording density in the axis direction of a recording medium (not shown). As the materials of the lower magnetic shield 71 and the upper magnetic shield 75, there may be used NiFe, FeN and so forth.
The lower gap film 72 and the upper gap film 74 made of the non-magnetic conductive materials can function to magnetically separate the lower magnetic shield 71, the upper magnetic shield 75 and the GMR element 73 from each other. The GMR head which includes the CIP type GMR element needs an insulating material such as an alumina as the gap film in order to insulate the magnetic shield and the GMR element from each other. On the other hand, the GMR head which includes the CPP type GMR element uses the conductive materials as the lower and upper magnetic gap films 72 and 74 in order to enable the sense current to flow through the lower and upper magnetic gap films 72 and 74 to the GMR element 73. Au, Cu, Ta and so forth, for example, may be used as the conductive materials of the lower and upper magnetic gap films 72 and 74.
When the signal magnetic field entered into the GMR element 73 from the recording medium (not shown) is changed, an electric resistance of the GMR element 73 also is changed in response to the change of the signal magnetic field. At that very time, when the current (sense current) is flowing through the GMR element 73, it is possible to detect the change of the electric resistance as an output.
The insulating films 76 between the GMR element 73 and the hard magnetic film 77 should preferably be made as thin as possible from the standpoint of a stabilizing magnetic field applied to the GMR element 73.
If the insulating films 76 are thick, then a spacing loss occurs in the stabilizing magnetic field which is applied from the hard magnetic film 77 to the magnetization free layer of the GMR element 73 and the GMR element 73 cannot be stabilized sufficiently. As a consequence, there occur various defects such as a Barkhausen noise and a hysteresis noise.
Having considered the dispersions of the film deposited states in the process in which the insulating films 76 are deposited and the number of processes increased when the insulating films 76 are deposited, if possible, the insulating films 76 should preferably be removed.
With respect to the spacing loss caused by the insulating films between the GMR element and the hard magnetic film, let us examine this spacing loss in accordance with a simulation.
As shown in FIG. 3, there was employed a simulation model in which hard magnetic films (hard films) 83 are disposed on the right and left of a GMR element 81 having a width W1 of 100 namometers through an insulating film 82 made of Al2O3. There, while spacing amount d provided by the insulating film 82 were being changed, we had calculated distributions of magnetic fields within the GMR element 81 for the spacing amounts d.
FIG. 4 shows results obtained from such calculations. The longitudinal axis of FIG. 4 represents a strength of a magnetic field normalized under the state in which strengths of magnetic fields obtained at respective ends (position at which an equality of x=50 nm is satisfied) of the GMR element 81 by the hard magnetic films 83 are assumed to be an ideal value 1 obtained when the hard magnetic films 83 are brought in direct contact with the GMR element 81 without the insulating films. In FIG. 4, due to the influences exerted by the calculation method, the value obtained at the position in which the equality of x=50 nm is satisfied when d=0 is not equal to the ideal value 1.
FIG. 5 shows the manner in which the strengths of the magnetic fields normalized at the central portion of the GMR element 81 are changed. The longitudinal axis of FIG. 5 shows the strengths of the magnetic fields normalized in the state where the strength of the magnetic field (about 0.17 in FIG. 4) obtained at the central portion of the GMR element 81, i.e., at the position in which an equality of x=0 is satisfied with the spacing amount d=0 is satisfied is assumed to be 1.
A study of FIGS. 4 and 5 reveals that the stabilizing magnetic field within the GMR element 81 can be reduced as the spacing amounts d, provided by the insulating film 82, increase.
In view of the aforesaid aspect, it is an object of the present invention to provide a giant magneto-resistive effect element and a highly-reliable magneto-resistive effect type head, a highly-reliable thin-film magnetic memory and a highly-reliable thin-film magnetic sensor including this giant magneto-resistive effect element in with a giant magneto-resistive effect element can sufficiently be stabilized magnetically.
It is another object of the present invention to provide a giant magneto-resistive effect element and a highly-reliable magneto-resistive effect type head, a highly-reliable thin-film magnetic memory and a highly-reliable thin-film magnetic sensor including this giant magneto-resistive effect element in which a manufacturing process can be simplified by reducing the number of processes.
It is a further object of the present invention to provide a giant magneto-resistive effect element and a magneto-resistive effect type head, a thin-film magnetic memory and a thin-film magnetic sensor including this giant magneto-resistive effect element which can be made highly reliable by suppressing dispersions in the manufacturing process and an electromigration.
According to an aspect of the present invention, there is provided a giant magneto-resistive effect element comprising a laminated layer film including a ferromagnetic film, a non-magnetic film and an anti-ferromagnetic film and in which a current is caused to flow in the direction perpendicular to the film plane of the laminated layer film by upper electrodes and lower electrodes. This giant magneto-resistive effect element is comprised of hard magnetic films directly connected to both sides in the width direction of the laminated layer film, insulating layers formed above or under the hard magnetic films and an opening defined between the insulating films of both sides to restrict a current path between the upper electrodes or the lower electrodes and the laminated layer film, wherein the hard magnetic films have a specific resistance which is substantially the same as or larger than that of the laminate layer film.
According to another aspect of the present invention, there is provided a magneto-resistive effect type head including a giant magneto-resistive effect element comprising a laminated layer film including a ferromagnetic film, a non-magnetic film and an anti-ferromagnetic film and in which a current is caused to flow in the direction perpendicular to the film plane of the laminated layer film by upper electrodes and lower electrodes, the giant magneto-resistive effect element, hard magnetic films directly connected to both sides in the width direction of the laminated layer film, insulating layers formed above or under the hard magnetic films and an opening defined between the insulating films of both sides to restrict a current path between the upper electrodes or the lower electrodes and the laminated layer film. This magneto-resistive effect type head is comprised of magnetic shields disposed so as to vertically sandwich the giant magneto-resistive effect element through a gap film made of a non-magnetic conductive material, wherein the gap film and the magnetic shields constitute the upper electrodes and the lower electrodes and the gap film serving also as the upper electrodes or the lower electrodes and the laminated layer film are electrically connected to each other through the opening defined between the insulating layers of both sides.
In accordance with a further aspect of the present invention, there is provided a thin-film magnetic memory which is comprised of a bit line, a word line and a giant magneto-resistive effect element comprising a laminated layer film including a ferromagnetic film, a non-magnetic film and an anti-ferromagnetic film and in which a current is caused to flow in the direction perpendicular to the film plane of the laminated layer film by upper electrodes and lower electrodes, hard magnetic films having a specific resistance substantially the same as or larger than that of the laminated layer film are disposed at both sides in the width direction of the laminated layer film, insulating layers are formed above or under the hard magnetic films, and a current path between the upper electrodes or the lower electrodes and the laminated layer film is restricted by an opening defined between the insulating layers of both sides, wherein a memory cell having the giant magneto-resistive effect element is disposed corresponding to an intersection between the bit line and the word line.
In accordance with yet a further aspect of the present invention, there is provided a thin-film magnetic sensor which is comprised of a giant magneto-resistive effect element which comprises a laminated layer film including a ferromagnetic film, a non-magnetic film and an anti-ferromagnetic film and in which a current is caused to flow in the direction perpendicular to the film plane of the laminated layer film by upper electrodes and lower electrodes, hard magnetic films having a specific resistance substantially the same as or larger than that of the laminated layer film are disposed at both sides in the width direction of the laminated layer film, insulating layers are formed above or under the hard magnetic films, and a current path between the upper electrodes or the lower electrodes and the laminated layer film is restricted by an opening defined between the insulating layers of both sides and magnetic shields disposed so as to vertically sandwich the giant magneto-resistive effect element through a gap film made of a non-magnetic conductive material, wherein the gap film and the magnetic shields constitute the upper electrodes and the lower electrodes and the gap film serving also as the upper electrodes or the lower electrodes and the laminated layer film are electrically connected to each other through an opening defined between the insulating layers of both sides.
According to the above-mentioned arrangement of the giant magneto-resistive effect element of the present invention, since the insulating layers are formed above or under the hard magnetic films and the current path between the upper electrodes or the lower electrodes and the laminated layer film is restricted by the opening defied between the insulating layers of both sides, the current which flows through the laminated layer film (giant magneto-resistive effect element) can be deviated to flow to the central portion.
In addition, since the hard magnetic films have the specific resistance which is substantially the same as or large than that of the laminated layer film, the current can selectively flow through the laminated layer film so that the current can be suppressed from being leaked into the hard magnetic films.
Since the hard magnetic films are directly connected to the laminated layer film, the stabilizing magnetic field from the hard magnetic films acts on the giant magneto-resistive effect element strongly so that operations of the giant magneto-resistive effect element, i.e., the change of the resistance can be stabilized.
According to the above-mentioned arrangement of the magneto-resistive effect type head of the present invention, since this magneto-resistive effect type head includes the above giant magneto-resistive effect element of the present invention, the stabilizing magnetic field from the hard magnetic films acts on the giant magneto-resistive effect element strongly and the change of the resistance of the giant magneto-resistive effect element is stabilized. Therefore, there can be obtained the stable signal output in response to the signal magnetic filed from the recording medium.
Further, according to the above-mentioned arrangement of the thin-film magnetic memory of the present invention, since this thin-film magnetic memory includes the above giant magneto-resistive effect element of the present invention, the stabilizing magnetic field from the hard magnetic films acts on the giant magneto-resistive effect element strongly and the change of the resistance of the giant magneto-resistive effect element in the memory cell is stabilized. Therefore, information can be written in the giant magneto-resistive effect element of the memory cell stably and recorded information can be read out from the giant magneto-resistive effect element of the memory call stably.
Furthermore, according to the above-mentioned arrangement of the thin-film magnetic sensor of the present invention, since this thin-film magnetic sensor includes the above giant magneto-resistive effect element of the present invention, the stabilizing magnetic field from the hard magnetic films acts on the giant magneto-resistive effect element strongly and the change of the resistive of the giant magneto-resistive effect element is stabilized. Therefore, there can be obtained the stable signal output in response to the external magnetic field.